Noise dose is computed using Table G-16a as follows:
When the sound level, L, is constant over the entire work shift, the noise dose, D, in percent, is given by: D=100 C/T where C is the total length of the work day, in hours, and T is the reference duration corresponding to the measured sound level, L, as given in Table G-16a or by the formula shown as a footnote to that table
When the workshift noise exposure is composed of two or more periods of noise at different levels, the total noise dose over the work day is given by:
D = 100 (C(1)/T(1) + C(2)/T(2) + ... + C(n)/T(n)),
where C(n) indicates the total time of exposure at a specific noise level, and T(n) indicates the reference duration for that level as given by Table G-16a
The eight-hour time-weighted average sound level (TWA), in decibels, may be computed from the dose, in percent, by means of the formula: TWA = 16.61 log(10) (D/100) + 90. For an eight-hour workshift with the noise level constant over the entire shift, the TWA is equal to the measured sound level
A table relating dose and TWA is given in Section II.
In the above table the reference duration, T, is computed bywhere L is the measured A-weighted sound level.
Conversion Between "Dose" and "8-Hour Time-Weighted Average"
Sound Level
Compliance with paragraphs (c)-(r) of this regulation is determined by the amount of exposure to noise in the workplace. The amount of such exposure is usually measured with an audiodosimeter which gives a readout in terms of "dose." In order to better understand the requirements of the amendment, dosimeter readings can be converted to an "8-hour time-weighted average sound level." (TWA).
In order to convert the reading of a dosimeter into TWA, see Table A-1, below. This table applies to dosimeters that are set by the manufacturer to calculate dose or percent exposure according to the relationships in Table G-16a. So, for example, a dose of 91 percent over an eight hour day results in a TWA of 89.3 dB, and, a dose of 50 percent corresponds to a TWA of 85 dB
If the dose as read on the dosimeter is less than or greater than the values found in Table A-1, the TWA may be calculated by using the formula: TWA = 16.61 log(10) (D/100) + 90 where TWA=8-hour time-weighted average sound level and D = accumulated dose in percent exposure.
TABLE A-1 - CONVERSION FROM "PERCENT NOISE EXPOSURE"
OR "DOSE" TO "8-HOUR TIME-WEIGHTED
AVERAGE SOUND LEVEL" (TWA)
Dose or percent noise exposure
TWA
10
73.4
15
76.3
20
78.4
25
80.0
30
81.3
35
82.4
40
83.4
45
84.2
50
85.0
55
85.7
60
86.3
65
86.9
70
87.4
75
87.9
80
88.4
81
88.5
82
88.6
83
88.7
84
88.7
85
88.8
86
88.9
87
89.0
88
89.1
89
89.2
90
89.2
91
89.3
92
89.4
93
89.5
94
89.6
95
89.6
96
89.7
97
89.8
98
89.9
99
89.9
100
90.0
101
90.1
102
90.1
103
90.2
104
90.3
105
90.4
106
90.4
107
90.5
108
90.6
109
90.6
110
90.7
111
90.8
112
90.8
113
90.9
114
90.9
115
91.1
116
91.1
117
91.1
118
91.2
119
91.3
120
91.3
125
91.6
130
91.9
135
92.2
140
92.4
145
92.7
150
92.9
155
93.2
160
93.4
165
93.6
170
93.8
175
94.0
180
94.2
185
94.4
190
94.6
195
94.8
200
95.0
210
95.4
220
95.7
230
96.0
240
96.3
250
96.6
260
96.9
270
97.2
280
97.4
290
97.7
300
97.9
310
98.2
320
98.4
330
98.6
340
98.8
350
99.0
360
99.2
370
99.4
380
99.6
390
99.8
400
100.0
410
100.2
420
100.4
430
100.5
440
100.7
450
100.8
460
101.0
470
101.2
480
101.3
490
101.5
500
101.6
510
101.8
520
101.9
530
102.0
540
102.2
550
102.3
560
102.4
570
102.6
580
102.7
590
102.8
600
102.9
610
103.0
620
103.2
630
103.3
640
103.4
650
103.5
660
103.6
670
103.7
680
103.8
690
103.9
700
104.0
710
104.1
720
104.2
730
104.3
740
104.4
750
104.5
760
104.6
770
104.7
780
104.8
790
104.9
800
105.0
810
105.1
820
105.2
830
105.3
840
105.4
850
105.4
860
105.5
870
105.6
880
105.7
890
105.8
900
105.8
910
105.9
920
106.0
930
106.1
940
106.2
950
106.2
960
106.3
970
106.4
980
106.5
990
106.5
999
106.6
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if they are exposed to average noise levels of 85 dB or greater during an 8 hour workday. In order to determine if exposures are at or above this level, it may ...
